[core] add CrossfadeParameters and dynamically bind pattern vertex buffers

7 files changed, 57 insertions, 30 deletions

diff --git a/src/mbgl/programs/line_program.cpp b/src/mbgl/programs/line_program.cpp
index 205f615264..1771cf8b03 100644
--- a/src/mbgl/programs/line_program.cpp
+++ b/src/mbgl/programs/line_program.cpp
@@ -87,13 +87,9 @@ LinePatternProgram::uniformValues(const RenderLinePaintProperties::PossiblyEvalu
                                   const TransformState& state,
                                   const std::array<float, 2>& pixelsToGLUnits,
                                   const Size atlasSize,
-                                  const Faded<std::string> pattern,
+                                  const CrossfadeParameters crossfade,
                                   const float pixelRatio) {
     
-    const auto linepattern = properties.get<LinePattern>();
-    // TODO get real crossfade values
-    const auto linePatternValue = linepattern.constantOr(mbgl::Faded<std::basic_string<char> >{ "", "", 1.0f, 2.0f, 1.0f});
-
     const auto tileRatio = 1 / tile.id.pixelsToTileUnits(1, state.getIntegerZoom());
 
     return makeValues<LinePatternProgram::UniformValues>(
@@ -101,9 +97,9 @@ LinePatternProgram::uniformValues(const RenderLinePaintProperties::PossiblyEvalu
         tile,
         state,
         pixelsToGLUnits,
-        uniforms::u_scale::Value{ {{ pixelRatio, tileRatio, pattern.fromScale, pattern.toScale}}  },
+        uniforms::u_scale::Value{ {{ pixelRatio, tileRatio, crossfade.fromScale, crossfade.toScale}}  },
         uniforms::u_texsize::Value{ atlasSize },
-        uniforms::u_fade::Value{ linePatternValue.t },
+        uniforms::u_fade::Value{ crossfade.t },
         uniforms::u_image::Value{ 0 }
     );
 }
diff --git a/src/mbgl/programs/line_program.hpp b/src/mbgl/programs/line_program.hpp
index f6fe5c09c8..9707778f26 100644
--- a/src/mbgl/programs/line_program.hpp
+++ b/src/mbgl/programs/line_program.hpp
@@ -121,7 +121,7 @@ public:
                                        const TransformState&,
                                        const std::array<float, 2>& pixelsToGLUnits,
                                        Size atlasSize,
-                                       const Faded<std::string> pattern,
+                                       const CrossfadeParameters crossfade,
                                        const float pixelRatio);
 };
 
diff --git a/src/mbgl/renderer/image_atlas.hpp b/src/mbgl/renderer/image_atlas.hpp
index 56c47e19a0..3af31a75f8 100644
--- a/src/mbgl/renderer/image_atlas.hpp
+++ b/src/mbgl/renderer/image_atlas.hpp
@@ -30,6 +30,12 @@ public:
         }};
     }
 
+    std::array<uint16_t, 4> tlbr() const {
+        const auto _tl = tl();
+        const auto _br = br();
+        return {{ _tl[0], _tl[1], _br[0], _br[1] }};
+    }
+
     std::array<float, 2> displaySize() const {
         return {{
             textureRect.w / pixelRatio,
diff --git a/src/mbgl/renderer/layers/render_line_layer.cpp b/src/mbgl/renderer/layers/render_line_layer.cpp
index 1ba94f6eef..aa84edfcb5 100644
--- a/src/mbgl/renderer/layers/render_line_layer.cpp
+++ b/src/mbgl/renderer/layers/render_line_layer.cpp
@@ -56,6 +56,8 @@ void RenderLineLayer::evaluate(const PropertyEvaluationParameters& parameters) {
     evaluated = RenderLinePaintProperties::PossiblyEvaluated(
         unevaluated.evaluate(parameters).concat(extra.evaluate(dashArrayParams)));
 
+    crossfade = parameters.getCrossfadeParameters();
+
     passes = (evaluated.get<style::LineOpacity>().constantOr(1.0) > 0
               && evaluated.get<style::LineColor>().constantOr(Color::black()).a > 0
               && evaluated.get<style::LineWidth>().constantOr(1.0) > 0)
@@ -83,7 +85,7 @@ void RenderLineLayer::render(PaintParameters& parameters, RenderSource*) {
 
             const auto& paintPropertyBinders = bucket.paintPropertyBinders.at(getID());
 
-            paintPropertyBinders.setConstantPatternPositions(patternPositionA, patternPositionB);
+            paintPropertyBinders.setPatternParameters(patternPositionA, patternPositionB, crossfade);
 
             const auto allUniformValues = programInstance.computeAllUniformValues(
                 std::move(uniformValues),
@@ -114,8 +116,9 @@ void RenderLineLayer::render(PaintParameters& parameters, RenderSource*) {
         };
         const auto linepattern = evaluated.get<LinePattern>();
         // TODO get real crossfade parameters
-        // need a placeholder value that will trigger line pattern program if the line-pattern value is non-constant
-        const auto linePatternValue = linepattern.constantOr(mbgl::Faded<std::basic_string<char> >{ "temp", "temp", 0.5f, 1.0f, 1.0f});
+        // need a non-empty placeholder value that will result in the LinePattern program to be
+        // used if the line-pattern value is non-constant
+        const auto linePatternValue = linepattern.constantOr(mbgl::Faded<std::basic_string<char> >{ "temp", "temp", 0.0f, 0.0f, 0.0f});
 
         if (!evaluated.get<LineDasharray>().from.empty()) {
             const LinePatternCap cap = bucket.layout.get<LineCap>() == LineCapType::Round
@@ -152,7 +155,7 @@ void RenderLineLayer::render(PaintParameters& parameters, RenderSource*) {
                      parameters.state,
                      parameters.pixelsToGLUnits,
                      texsize,
-                     linePatternValue,
+                     crossfade,
                      parameters.pixelRatio),
                      *posA,
                      *posB));
diff --git a/src/mbgl/renderer/layers/render_line_layer.hpp b/src/mbgl/renderer/layers/render_line_layer.hpp
index 7694466e41..e02e7e6b03 100644
--- a/src/mbgl/renderer/layers/render_line_layer.hpp
+++ b/src/mbgl/renderer/layers/render_line_layer.hpp
@@ -5,7 +5,6 @@
 #include <mbgl/style/layers/line_layer_properties.hpp>
 #include <mbgl/programs/uniforms.hpp>
 #include <mbgl/style/image_impl.hpp>
-#include <mbgl/style/image_impl.hpp>
 
 namespace mbgl {
 
@@ -54,6 +53,7 @@ public:
 
 private:
     float getLineWidth(const GeometryTileFeature&, const float) const;
+    CrossfadeParameters crossfade;
     PremultipliedImage colorRamp;
     optional<gl::Texture> colorRampTexture;
 };
diff --git a/src/mbgl/renderer/paint_property_binder.hpp b/src/mbgl/renderer/paint_property_binder.hpp
index 96b1f14d3e..cf3f9716df 100644
--- a/src/mbgl/renderer/paint_property_binder.hpp
+++ b/src/mbgl/renderer/paint_property_binder.hpp
@@ -84,7 +84,7 @@ public:
 
     virtual void populateVertexVector(const GeometryTileFeature& feature, std::size_t length, const ImagePositions&) = 0;
     virtual void upload(gl::Context& context) = 0;
-    virtual void setConstantPatternPositions(const optional<ImagePosition>&, const optional<ImagePosition>&) = 0;
+    virtual void setPatternParameters(const optional<ImagePosition>&, const optional<ImagePosition>&, CrossfadeParameters&) = 0;
     virtual std::tuple<ExpandToType<As, optional<gl::AttributeBinding>>...> attributeBinding(const PossiblyEvaluatedType& currentValue) const = 0;
     virtual std::tuple<ExpandToType<As, float>...> interpolationFactor(float currentZoom) const = 0;
     virtual std::tuple<ExpandToType<As, UniformValueType>...> uniformValue(const PossiblyEvaluatedType& currentValue) const = 0;
@@ -103,7 +103,7 @@ public:
 
     void populateVertexVector(const GeometryTileFeature&, std::size_t, const ImagePositions&) override {}
     void upload(gl::Context&) override {}
-    void setConstantPatternPositions(const optional<ImagePosition>&, const optional<ImagePosition>&) override {};
+    void setPatternParameters(const optional<ImagePosition>&, const optional<ImagePosition>&, CrossfadeParameters&) override {};
 
     std::tuple<optional<gl::AttributeBinding>> attributeBinding(const PossiblyEvaluatedPropertyValue<T>&) const override {
         return std::tuple<optional<gl::AttributeBinding>> {};
@@ -131,11 +131,11 @@ public:
     void populateVertexVector(const GeometryTileFeature&, std::size_t, const ImagePositions&) override {}
     void upload(gl::Context&) override {}
 
-    void setConstantPatternPositions(const optional<ImagePosition>& posA, const optional<ImagePosition>& posB) override {
+    void setPatternParameters(const optional<ImagePosition>& posA, const optional<ImagePosition>& posB, CrossfadeParameters&) override {
         if (!posA && !posB) {
             return;
         } else {
-            constantPatternPositions = std::tuple<std::array<uint16_t, 4>, std::array<uint16_t, 4>> { {{posB->tl()[0], posB->tl()[1], posB->br()[0], posB->br()[1]}}, {{posA->tl()[0], posA->tl()[1], posA->br()[0], posA->br()[1]}} };
+            constantPatternPositions = std::tuple<std::array<uint16_t, 4>, std::array<uint16_t, 4>> { posB->tlbr(), posA->tlbr() };
         }
     }
 
@@ -168,7 +168,7 @@ public:
         : expression(std::move(expression_)),
           defaultValue(std::move(defaultValue_)) {
     }
-    void setConstantPatternPositions(const optional<ImagePosition>&, const optional<ImagePosition>&) override {};
+    void setPatternParameters(const optional<ImagePosition>&, const optional<ImagePosition>&, CrossfadeParameters&) override {};
     void populateVertexVector(const GeometryTileFeature& feature, std::size_t length, const ImagePositions&) override {
         auto evaluated = expression.evaluate(feature, defaultValue);
         this->statistics.add(evaluated);
@@ -223,7 +223,7 @@ public:
           defaultValue(std::move(defaultValue_)),
           zoomRange({zoom, zoom + 1}) {
     }
-    void setConstantPatternPositions(const optional<ImagePosition>&, const optional<ImagePosition>&) override {};
+    void setPatternParameters(const optional<ImagePosition>&, const optional<ImagePosition>&, CrossfadeParameters&) override {};
     void populateVertexVector(const GeometryTileFeature& feature, std::size_t length, const ImagePositions&) override {
         Range<T> range = expression.evaluate(zoomRange, feature, defaultValue);
         this->statistics.add(range.min);
@@ -295,7 +295,9 @@ public:
           zoomRange({zoom, zoom + 1}) {
     }
 
-    void setConstantPatternPositions(const optional<ImagePosition>&, const optional<ImagePosition>&) override {};
+    void setPatternParameters(const optional<ImagePosition>&, const optional<ImagePosition>&, CrossfadeParameters& crossfade_) override {
+        crossfade = crossfade_;
+    };
 
     void populateVertexVector(const GeometryTileFeature& feature, std::size_t length, const ImagePositions& patternPositions) override {
         std::array<T, 3> range;
@@ -318,14 +320,10 @@ public:
             const ImagePosition imageMid = mid->second;
             const ImagePosition imageMax = max->second;
 
-            const BaseAttributeValue patternTo = {{ imageMid.tl()[0], imageMid.tl()[1], imageMid.br()[0], imageMid.br()[1] }};
-            const BaseAttributeValue2 patternFromZoomIn = {{ imageMin.tl()[0], imageMin.tl()[1], imageMin.br()[0], imageMin.br()[1] }};
-            const BaseAttributeValue2 patternFromZoomOut = {{ imageMax.tl()[0], imageMax.tl()[1], imageMax.br()[0], imageMax.br()[1] }};
-
             for (std::size_t i = zoomInVertexVector.vertexSize(); i < length; ++i) {
-                patternToVertexVector.emplace_back(Vertex { patternTo });
-                zoomInVertexVector.emplace_back(Vertex2 { patternFromZoomIn });
-                zoomOutVertexVector.emplace_back(Vertex2 { patternFromZoomOut });
+                patternToVertexVector.emplace_back(Vertex { imageMid.tlbr() });
+                zoomInVertexVector.emplace_back(Vertex2 { imageMin.tlbr() });
+                zoomOutVertexVector.emplace_back(Vertex2 { imageMax.tlbr() });
             }
         }
     }
@@ -340,7 +338,11 @@ public:
         if (currentValue.isConstant()) {
             return {};
         } else {
-            return std::tuple<optional<gl::AttributeBinding>, optional<gl::AttributeBinding>> { AttributeType::binding(*patternToVertexBuffer, 0, BaseAttribute::Dimensions), AttributeType2::binding(*zoomInVertexBuffer, 0, BaseAttribute2::Dimensions) };
+            return std::tuple<optional<gl::AttributeBinding>, optional<gl::AttributeBinding>> {
+                AttributeType::binding(*patternToVertexBuffer, 0, BaseAttribute::Dimensions),
+                AttributeType2::binding(
+                    crossfade.fromScale == 2 ? *zoomInVertexBuffer : *zoomOutVertexBuffer,
+                    0, BaseAttribute2::Dimensions) };
         }
     }
 
@@ -363,6 +365,7 @@ private:
     optional<gl::VertexBuffer<Vertex>> patternToVertexBuffer;
     optional<gl::VertexBuffer<Vertex2>> zoomInVertexBuffer;
     optional<gl::VertexBuffer<Vertex2>> zoomOutVertexBuffer;
+    CrossfadeParameters crossfade;
 };
 
 template <class T, class PossiblyEvaluatedType>
@@ -461,9 +464,9 @@ public:
         });
     }
 
-    void setConstantPatternPositions(const optional<ImagePosition>& posA, const optional<ImagePosition>& posB) const {
+    void setPatternParameters(const optional<ImagePosition>& posA, const optional<ImagePosition>& posB, CrossfadeParameters& crossfade) const {
         util::ignore({
-            (binders.template get<Ps>()->setConstantPatternPositions(posA, posB), 0)...
+            (binders.template get<Ps>()->setPatternParameters(posA, posB, crossfade), 0)...
         });
     }
 
diff --git a/src/mbgl/renderer/property_evaluation_parameters.hpp b/src/mbgl/renderer/property_evaluation_parameters.hpp
index da6a4a0892..0e1c317294 100644
--- a/src/mbgl/renderer/property_evaluation_parameters.hpp
+++ b/src/mbgl/renderer/property_evaluation_parameters.hpp
@@ -5,6 +5,13 @@
 
 namespace mbgl {
 
+class CrossfadeParameters {
+public:
+    float fromScale;
+    float toScale;
+    float t;
+};
+
 class PropertyEvaluationParameters {
 public:
     explicit PropertyEvaluationParameters(float z_)
@@ -24,6 +31,18 @@ public:
           defaultFadeDuration(std::move(defaultFadeDuration_)),
           useIntegerZoom(useIntegerZoom_) {}
 
+    CrossfadeParameters getCrossfadeParameters() const {
+        const float fraction = z - std::floor(z);
+        const std::chrono::duration<float> d = defaultFadeDuration;
+        const float t = d != std::chrono::duration<float>::zero()
+                ? std::min((now - zoomHistory.lastIntegerZoomTime) / d, 1.0f)
+                : 1.0f;
+
+        return z > zoomHistory.lastIntegerZoom
+            ? CrossfadeParameters { 2.0f, 1.0f, fraction + (1.0f - fraction) * t }
+            : CrossfadeParameters { 0.5f, 1.0f, 1 - (1 - t) * fraction };
+    }
+
     float z;
     TimePoint now;
     ZoomHistory zoomHistory;